* java-tree.h (push_labeled_block, pop_labeled_block): Remove.

[pf3gnuchains/gcc-fork.git] / gcc / tree-ssa-forwprop.c

diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c
index cbf1fde..cac5d0a 100644 (file)
--- a/gcc/tree-ssa-forwprop.c
+++ b/gcc/tree-ssa-forwprop.c
@@ -1,11 +1,11 @@
-/* Forward propagation of single use variables.
-   Copyright (C) 2004 Free Software Foundation, Inc.
+/* Forward propagation of expressions for single use variables.
+   Copyright (C) 2004, 2005, 2007 Free Software Foundation, Inc.

 
 This file is part of GCC.
 
 GCC is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by
 
 This file is part of GCC.
 
 GCC is free software; you can redistribute it and/or modify
 it under the terms of the GNU General Public License as published by

-the Free Software Foundation; either version 2, or (at your option)
+the Free Software Foundation; either version 3, or (at your option)

 any later version.
 
 GCC is distributed in the hope that it will be useful,
 any later version.
 
 GCC is distributed in the hope that it will be useful,


@@ -14,15 +14,13 @@ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License
 GNU General Public License for more details.
 
 You should have received a copy of the GNU General Public License

-along with GCC; see the file COPYING.  If not, write to
-the Free Software Foundation, 59 Temple Place - Suite 330,
-Boston, MA 02111-1307, USA.  */
+along with GCC; see the file COPYING3.  If not see
+<http://www.gnu.org/licenses/>.  */

 
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
 #include "tm.h"
 
 #include "config.h"
 #include "system.h"
 #include "coretypes.h"
 #include "tm.h"

-#include "errors.h"

 #include "ggc.h"
 #include "tree.h"
 #include "rtl.h"
 #include "ggc.h"
 #include "tree.h"
 #include "rtl.h"


@@ -33,13 +31,21 @@ Boston, MA 02111-1307, USA.  */
 #include "tree-flow.h"
 #include "tree-pass.h"
 #include "tree-dump.h"
 #include "tree-flow.h"
 #include "tree-pass.h"
 #include "tree-dump.h"

+#include "langhooks.h"
+#include "flags.h"

 
 

-/* This pass performs simple forward propagation of single use variables
-   from their definition site into their single use site.
+/* This pass propagates the RHS of assignment statements into use
+   sites of the LHS of the assignment.  It's basically a specialized
+   form of tree combination.   It is hoped all of this can disappear
+   when we have a generalized tree combiner.

 
 

-   Right now we only bother forward propagating into COND_EXPRs since those
-   are relatively common cases where forward propagation creates valid
-   gimple code without the expression needing to fold.  i.e.
+   Note carefully that after propagation the resulting statement
+   must still be a proper gimple statement.  Right now we simply
+   only perform propagations we know will result in valid gimple
+   code.  One day we'll want to generalize this code.
+
+   One class of common cases we handle is forward propagating a single use
+   variable into a COND_EXPR.  

 
      bb0:
        x = a COND b;
 
      bb0:
        x = a COND b;


@@ -100,459 +106,1264 @@ Boston, MA 02111-1307, USA.  */
 
    In addition to eliminating the variable and the statement which assigns
    a value to the variable, we may be able to later thread the jump without
 
    In addition to eliminating the variable and the statement which assigns
    a value to the variable, we may be able to later thread the jump without

-   adding insane complexity in the dominator optimizer. 
+   adding insane complexity in the dominator optimizer.

 
    Also note these transformations can cascade.  We handle this by having
    a worklist of COND_EXPR statements to examine.  As we make a change to
    a statement, we put it back on the worklist to examine on the next
    iteration of the main loop.
 
 
    Also note these transformations can cascade.  We handle this by having
    a worklist of COND_EXPR statements to examine.  As we make a change to
    a statement, we put it back on the worklist to examine on the next
    iteration of the main loop.
 

+   A second class of propagation opportunities arises for ADDR_EXPR
+   nodes.
+
+     ptr = &x->y->z;
+     res = *ptr;
+
+   Will get turned into
+
+     res = x->y->z;
+
+   Or
+
+     ptr = &x[0];
+     ptr2 = ptr + <constant>;
+
+   Will get turned into
+
+     ptr2 = &x[constant/elementsize];
+
+  Or
+
+     ptr = &x[0];
+     offset = index * element_size;
+     offset_p = (pointer) offset;
+     ptr2 = ptr + offset_p
+
+  Will get turned into:
+
+     ptr2 = &x[index];
+
+  We also propagate casts into SWITCH_EXPR and COND_EXPR conditions to
+  allow us to remove the cast and {NOT_EXPR,NEG_EXPR} into a subsequent
+  {NOT_EXPR,NEG_EXPR}.
+

    This will (of course) be extended as other needs arise.  */
 
    This will (of course) be extended as other needs arise.  */
 

-/* Bitmap of variables for which we want immediate uses.  This is set
-   by record_single_argument_cond_exprs and tested in need_imm_uses_for.  */
-static bitmap vars;
+static bool forward_propagate_addr_expr (tree name, tree rhs);
+
+/* Set to true if we delete EH edges during the optimization.  */
+static bool cfg_changed;
+
+
+/* Get the next statement we can propagate NAME's value into skipping
+   trivial copies.  Returns the statement that is suitable as a
+   propagation destination or NULL_TREE if there is no such one.
+   This only returns destinations in a single-use chain.  FINAL_NAME_P
+   if non-NULL is written to the ssa name that represents the use.  */
+
+static tree
+get_prop_dest_stmt (tree name, tree *final_name_p)
+{
+  use_operand_p use;
+  tree use_stmt;

 
 

-static bool need_imm_uses_for (tree);
-static void tree_ssa_forward_propagate_single_use_vars (void);
-static void record_single_argument_cond_exprs (varray_type,
-                                              varray_type *,
-                                              bitmap);
-static void substitute_single_use_vars (varray_type *, varray_type);
+  do {
+    /* If name has multiple uses, bail out.  */
+    if (!single_imm_use (name, &use, &use_stmt))
+      return NULL_TREE;

 
 

-/* Function indicating whether we ought to include information for 'var'
-   when calculating immediate uses.  */
+    /* If this is not a trivial copy, we found it.  */
+    if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT
+       || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) != SSA_NAME
+       || GIMPLE_STMT_OPERAND (use_stmt, 1) != name)
+      break;
+
+    /* Continue searching uses of the copy destination.  */
+    name = GIMPLE_STMT_OPERAND (use_stmt, 0);
+  } while (1);
+
+  if (final_name_p)
+    *final_name_p = name;
+
+  return use_stmt;
+}
+
+/* Get the statement we can propagate from into NAME skipping
+   trivial copies.  Returns the statement which defines the
+   propagation source or NULL_TREE if there is no such one.
+   If SINGLE_USE_ONLY is set considers only sources which have
+   a single use chain up to NAME.  If SINGLE_USE_P is non-null,
+   it is set to whether the chain to NAME is a single use chain
+   or not.  SINGLE_USE_P is not written to if SINGLE_USE_ONLY is set.  */
+
+static tree
+get_prop_source_stmt (tree name, bool single_use_only, bool *single_use_p)
+{
+  bool single_use = true;
+
+  do {
+    tree def_stmt = SSA_NAME_DEF_STMT (name);
+
+    if (!has_single_use (name))
+      {
+       single_use = false;
+       if (single_use_only)
+         return NULL_TREE;
+      }
+
+    /* If name is defined by a PHI node or is the default def, bail out.  */
+    if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
+      return NULL_TREE;
+
+    /* If name is not a simple copy destination, we found it.  */
+    if (TREE_CODE (GIMPLE_STMT_OPERAND (def_stmt, 1)) != SSA_NAME)
+      {
+       if (!single_use_only && single_use_p)
+         *single_use_p = single_use;
+
+       return def_stmt;
+      }
+
+    /* Continue searching the def of the copy source name.  */
+    name = GIMPLE_STMT_OPERAND (def_stmt, 1);
+  } while (1);
+}
+
+/* Checks if the destination ssa name in DEF_STMT can be used as
+   propagation source.  Returns true if so, otherwise false.  */

 
 static bool
 
 static bool

-need_imm_uses_for (tree var)
+can_propagate_from (tree def_stmt)
+{
+  tree rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
+
+  /* We cannot propagate ssa names that occur in abnormal phi nodes.  */
+  switch (TREE_CODE_LENGTH (TREE_CODE (rhs)))
+    {
+    case 3:
+      if (TREE_OPERAND (rhs, 2) != NULL_TREE
+         && TREE_CODE (TREE_OPERAND (rhs, 2)) == SSA_NAME
+         && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 2)))
+       return false;
+    case 2:
+      if (TREE_OPERAND (rhs, 1) != NULL_TREE
+         && TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
+         && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 1)))
+       return false;
+    case 1:
+      if (TREE_OPERAND (rhs, 0) != NULL_TREE
+         && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
+         && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (rhs, 0)))
+       return false;
+      break;
+
+    default:
+      return false;
+    }
+
+  /* If the definition is a conversion of a pointer to a function type,
+     then we can not apply optimizations as some targets require function
+     pointers to be canonicalized and in this case this optimization could
+     eliminate a necessary canonicalization.  */
+  if ((TREE_CODE (rhs) == NOP_EXPR
+       || TREE_CODE (rhs) == CONVERT_EXPR)
+      && POINTER_TYPE_P (TREE_TYPE (TREE_OPERAND (rhs, 0)))
+      && TREE_CODE (TREE_TYPE (TREE_TYPE
+                               (TREE_OPERAND (rhs, 0)))) == FUNCTION_TYPE)
+    return false;
+
+  return true;
+}
+
+/* Remove a copy chain ending in NAME along the defs but not
+   further or including UP_TO_STMT.  If NAME was replaced in
+   its only use then this function can be used to clean up
+   dead stmts.  Returns true if UP_TO_STMT can be removed
+   as well, otherwise false.  */
+
+static bool
+remove_prop_source_from_use (tree name, tree up_to_stmt)
+{
+  block_stmt_iterator bsi;
+  tree stmt;
+
+  do {
+    if (!has_zero_uses (name))
+      return false;
+
+    stmt = SSA_NAME_DEF_STMT (name);
+    if (stmt == up_to_stmt)
+      return true;
+
+    bsi = bsi_for_stmt (stmt);
+    release_defs (stmt);
+    bsi_remove (&bsi, true);
+
+    name = GIMPLE_STMT_OPERAND (stmt, 1);
+  } while (TREE_CODE (name) == SSA_NAME);
+
+  return false;
+}
+
+/* Combine OP0 CODE OP1 in the context of a COND_EXPR.  Returns
+   the folded result in a form suitable for COND_EXPR_COND or
+   NULL_TREE, if there is no suitable simplified form.  If
+   INVARIANT_ONLY is true only gimple_min_invariant results are
+   considered simplified.  */
+
+static tree
+combine_cond_expr_cond (enum tree_code code, tree type,
+                       tree op0, tree op1, bool invariant_only)

 {
 {

-  return bitmap_bit_p (vars, SSA_NAME_VERSION (var));
+  tree t;
+
+  gcc_assert (TREE_CODE_CLASS (code) == tcc_comparison);
+
+  t = fold_binary (code, type, op0, op1);
+  if (!t)
+    return NULL_TREE;
+
+  /* Require that we got a boolean type out if we put one in.  */
+  gcc_assert (TREE_CODE (TREE_TYPE (t)) == TREE_CODE (type));
+
+  /* For (bool)x use x != 0.  */
+  if (TREE_CODE (t) == NOP_EXPR
+      && TREE_TYPE (t) == boolean_type_node)
+    {
+      tree top0 = TREE_OPERAND (t, 0);
+      t = build2 (NE_EXPR, type,
+                 top0, build_int_cst (TREE_TYPE (top0), 0));
+    }
+  /* For !x use x == 0.  */
+  else if (TREE_CODE (t) == TRUTH_NOT_EXPR)
+    {
+      tree top0 = TREE_OPERAND (t, 0);
+      t = build2 (EQ_EXPR, type,
+                 top0, build_int_cst (TREE_TYPE (top0), 0));
+    }
+  /* For cmp ? 1 : 0 use cmp.  */
+  else if (TREE_CODE (t) == COND_EXPR
+          && COMPARISON_CLASS_P (TREE_OPERAND (t, 0))
+          && integer_onep (TREE_OPERAND (t, 1))
+          && integer_zerop (TREE_OPERAND (t, 2)))
+    {
+      tree top0 = TREE_OPERAND (t, 0);
+      t = build2 (TREE_CODE (top0), type,
+                 TREE_OPERAND (top0, 0), TREE_OPERAND (top0, 1));
+    }
+
+  /* Bail out if we required an invariant but didn't get one.  */
+  if (invariant_only
+      && !is_gimple_min_invariant (t))
+    return NULL_TREE;
+
+  /* A valid conditional for a COND_EXPR is either a gimple value
+     or a comparison with two gimple value operands.  */
+  if (is_gimple_val (t)
+      || (COMPARISON_CLASS_P (t)
+         && is_gimple_val (TREE_OPERAND (t, 0))
+         && is_gimple_val (TREE_OPERAND (t, 1))))
+    return t;
+
+  return NULL_TREE;

 }
 
 }
 

-/* Find all COND_EXPRs with a condition that is a naked SSA_NAME or
-   an equality comparison against a constant.
+/* Propagate from the ssa name definition statements of COND_EXPR
+   in statement STMT into the conditional if that simplifies it.
+   Returns zero if no statement was changed, one if there were
+   changes and two if cfg_cleanup needs to run.  */
+
+static int
+forward_propagate_into_cond (tree cond_expr, tree stmt)
+{
+  int did_something = 0;
+
+  do {
+    tree tmp = NULL_TREE;
+    tree cond = COND_EXPR_COND (cond_expr);
+    tree name, def_stmt, rhs;
+    bool single_use_p;
+
+    /* We can do tree combining on SSA_NAME and comparison expressions.  */
+    if (COMPARISON_CLASS_P (cond)
+       && TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME)
+      {
+       /* For comparisons use the first operand, that is likely to
+          simplify comparisons against constants.  */
+       name = TREE_OPERAND (cond, 0);
+       def_stmt = get_prop_source_stmt (name, false, &single_use_p);
+       if (def_stmt != NULL_TREE
+           && can_propagate_from (def_stmt))
+         {
+           tree op1 = TREE_OPERAND (cond, 1);
+           rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
+           tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
+                                         fold_convert (TREE_TYPE (op1), rhs),
+                                         op1, !single_use_p);
+         }
+       /* If that wasn't successful, try the second operand.  */
+       if (tmp == NULL_TREE
+           && TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME)
+         {
+           tree op0 = TREE_OPERAND (cond, 0);
+           name = TREE_OPERAND (cond, 1);
+           def_stmt = get_prop_source_stmt (name, false, &single_use_p);
+           if (def_stmt == NULL_TREE
+               || !can_propagate_from (def_stmt))
+             return did_something;
+
+           rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
+           tmp = combine_cond_expr_cond (TREE_CODE (cond), boolean_type_node,
+                                         op0,
+                                         fold_convert (TREE_TYPE (op0), rhs),
+                                         !single_use_p);
+         }
+      }
+    else if (TREE_CODE (cond) == SSA_NAME)
+      {
+       name = cond;
+       def_stmt = get_prop_source_stmt (name, true, NULL);
+       if (def_stmt == NULL_TREE
+           || !can_propagate_from (def_stmt))
+         return did_something;
+
+       rhs = GIMPLE_STMT_OPERAND (def_stmt, 1);
+       tmp = combine_cond_expr_cond (NE_EXPR, boolean_type_node, rhs,
+                                     build_int_cst (TREE_TYPE (rhs), 0),
+                                     false);
+      }
+
+    if (tmp)
+      {
+       if (dump_file && tmp)
+         {
+           fprintf (dump_file, "  Replaced '");
+           print_generic_expr (dump_file, cond, 0);
+           fprintf (dump_file, "' with '");
+           print_generic_expr (dump_file, tmp, 0);
+           fprintf (dump_file, "'\n");
+         }
+
+       COND_EXPR_COND (cond_expr) = unshare_expr (tmp);
+       update_stmt (stmt);

 
 

-   Record the identified COND_EXPRs and the SSA_NAME used in the COND_EXPR
-   into a virtual array, which is returned to the caller.  Also record
-   into VARS that we will need immediate uses for the identified SSA_NAME.
+       /* Remove defining statements.  */
+       remove_prop_source_from_use (name, NULL);

 
 

-   The more uninteresting COND_EXPRs and associated SSA_NAMEs we can
-   filter out here, the faster this pass will run since its runtime is
-   dominated by the time to build immediate uses.  */
+       if (is_gimple_min_invariant (tmp))
+         did_something = 2;
+       else if (did_something == 0)
+         did_something = 1;
+
+       /* Continue combining.  */
+       continue;
+      }
+
+    break;
+  } while (1);
+
+  return did_something;
+}
+
+/* We've just substituted an ADDR_EXPR into stmt.  Update all the 
+   relevant data structures to match.  */

 
 static void
 
 static void

-record_single_argument_cond_exprs (varray_type cond_worklist,
-                                  varray_type *vars_worklist,
-                                  bitmap vars)
+tidy_after_forward_propagate_addr (tree stmt)
+{
+  /* We may have turned a trapping insn into a non-trapping insn.  */
+  if (maybe_clean_or_replace_eh_stmt (stmt, stmt)
+      && tree_purge_dead_eh_edges (bb_for_stmt (stmt)))
+    cfg_changed = true;

 
 

+  if (TREE_CODE (GIMPLE_STMT_OPERAND (stmt, 1)) == ADDR_EXPR)
+     recompute_tree_invariant_for_addr_expr (GIMPLE_STMT_OPERAND (stmt, 1));
+
+  mark_symbols_for_renaming (stmt);
+}
+
+/* DEF_RHS contains the address of the 0th element in an array. 
+   USE_STMT uses type of DEF_RHS to compute the address of an
+   arbitrary element within the array.  The (variable) byte offset
+   of the element is contained in OFFSET.
+
+   We walk back through the use-def chains of OFFSET to verify that
+   it is indeed computing the offset of an element within the array
+   and extract the index corresponding to the given byte offset.
+
+   We then try to fold the entire address expression into a form
+   &array[index].
+
+   If we are successful, we replace the right hand side of USE_STMT
+   with the new address computation.  */
+
+static bool
+forward_propagate_addr_into_variable_array_index (tree offset,
+                                                 tree def_rhs, tree use_stmt)
+{
+  tree index;
+
+  /* Try to find an expression for a proper index.  This is either
+     a multiplication expression by the element size or just the
+     ssa name we came along in case the element size is one.  */
+  if (integer_onep (TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
+    index = offset;
+  else
+    {
+      /* Get the offset's defining statement.  */
+      offset = SSA_NAME_DEF_STMT (offset);
+
+      /* The statement which defines OFFSET before type conversion
+         must be a simple GIMPLE_MODIFY_STMT.  */
+      if (TREE_CODE (offset) != GIMPLE_MODIFY_STMT)
+       return false;
+
+      /* The RHS of the statement which defines OFFSET must be a
+        multiplication of an object by the size of the array elements. 
+        This implicitly verifies that the size of the array elements
+        is constant.  */
+     offset = GIMPLE_STMT_OPERAND (offset, 1);
+      if (TREE_CODE (offset) != MULT_EXPR
+         || TREE_CODE (TREE_OPERAND (offset, 1)) != INTEGER_CST
+         || !simple_cst_equal (TREE_OPERAND (offset, 1),
+                               TYPE_SIZE_UNIT (TREE_TYPE (TREE_TYPE (def_rhs)))))
+       return false;
+
+      /* The first operand to the MULT_EXPR is the desired index.  */
+      index = TREE_OPERAND (offset, 0);
+    }
+
+  /* Replace the pointer addition with array indexing.  */
+  GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
+  TREE_OPERAND (TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0), 1)
+    = index;
+
+  /* That should have created gimple, so there is no need to
+     record information to undo the propagation.  */
+  fold_stmt_inplace (use_stmt);
+  tidy_after_forward_propagate_addr (use_stmt);
+  return true;
+}
+
+/* NAME is a SSA_NAME representing DEF_RHS which is of the form
+   ADDR_EXPR <whatever>.
+
+   Try to forward propagate the ADDR_EXPR into the use USE_STMT.
+   Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
+   node or for recovery of array indexing from pointer arithmetic.
+   
+   Return true if the propagation was successful (the propagation can
+   be not totally successful, yet things may have been changed).  */
+
+static bool
+forward_propagate_addr_expr_1 (tree name, tree def_rhs, tree use_stmt,
+                              bool single_use_p)

 {
 {

-  /* The first pass over the blocks gathers the set of variables we need
-     immediate uses for as well as the set of interesting COND_EXPRs.
+  tree lhs, rhs, array_ref;
+
+  /* Strip away any outer COMPONENT_REF/ARRAY_REF nodes from the LHS. 
+     ADDR_EXPR will not appear on the LHS.  */
+  lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
+  while (handled_component_p (lhs))
+    lhs = TREE_OPERAND (lhs, 0);
+
+  rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);

 
 

-     A simpler implementation may be appropriate if/when we have a lower
-     overhead means of getting immediate use information.  */
-  while (VARRAY_ACTIVE_SIZE (cond_worklist) > 0)
+  /* Now see if the LHS node is an INDIRECT_REF using NAME.  If so, 
+     propagate the ADDR_EXPR into the use of NAME and fold the result.  */
+  if (TREE_CODE (lhs) == INDIRECT_REF && TREE_OPERAND (lhs, 0) == name)

     {
     {

-      tree last = VARRAY_TOP_TREE (cond_worklist);
+      /* This should always succeed in creating gimple, so there is
+        no need to save enough state to undo this propagation.  */
+      TREE_OPERAND (lhs, 0) = unshare_expr (def_rhs);
+      fold_stmt_inplace (use_stmt);
+      tidy_after_forward_propagate_addr (use_stmt);

 
 

-      VARRAY_POP (cond_worklist);
+      /* Continue propagating into the RHS.  */
+    }

 
 

-      /* See if this block ends in a COND_EXPR.  */
-      if (last && TREE_CODE (last) == COND_EXPR)
+  /* Trivial cases.  The use statement could be a trivial copy or a
+     useless conversion.  Recurse to the uses of the lhs as copyprop does
+     not copy through differen variant pointers and FRE does not catch
+     all useless conversions.  Treat the case of a single-use name and
+     a conversion to def_rhs type separate, though.  */
+  else if (TREE_CODE (lhs) == SSA_NAME
+          && (TREE_CODE (rhs) == NOP_EXPR
+              || TREE_CODE (rhs) == CONVERT_EXPR)
+          && TREE_TYPE (rhs) == TREE_TYPE (def_rhs)
+          && single_use_p)
+    {
+      GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (def_rhs);
+      return true;
+    }
+  else if ((TREE_CODE (lhs) == SSA_NAME
+           && rhs == name)
+          || ((TREE_CODE (rhs) == NOP_EXPR
+               || TREE_CODE (rhs) == CONVERT_EXPR)
+              && useless_type_conversion_p (TREE_TYPE (rhs),
+                                           TREE_TYPE (def_rhs))))
+    return forward_propagate_addr_expr (lhs, def_rhs);
+
+  /* Strip away any outer COMPONENT_REF, ARRAY_REF or ADDR_EXPR
+     nodes from the RHS.  */
+  while (handled_component_p (rhs)
+        || TREE_CODE (rhs) == ADDR_EXPR)
+    rhs = TREE_OPERAND (rhs, 0);
+
+  /* Now see if the RHS node is an INDIRECT_REF using NAME.  If so, 
+     propagate the ADDR_EXPR into the use of NAME and fold the result.  */
+  if (TREE_CODE (rhs) == INDIRECT_REF && TREE_OPERAND (rhs, 0) == name)
+    {
+      /* This should always succeed in creating gimple, so there is
+         no need to save enough state to undo this propagation.  */
+      TREE_OPERAND (rhs, 0) = unshare_expr (def_rhs);
+      fold_stmt_inplace (use_stmt);
+      tidy_after_forward_propagate_addr (use_stmt);
+      return true;
+    }
+
+  /* The remaining cases are all for turning pointer arithmetic into
+     array indexing.  They only apply when we have the address of
+     element zero in an array.  If that is not the case then there
+     is nothing to do.  */
+  array_ref = TREE_OPERAND (def_rhs, 0);
+  if (TREE_CODE (array_ref) != ARRAY_REF
+      || TREE_CODE (TREE_TYPE (TREE_OPERAND (array_ref, 0))) != ARRAY_TYPE
+      || !integer_zerop (TREE_OPERAND (array_ref, 1)))
+    return false;
+
+  /* If the use of the ADDR_EXPR is not a POINTER_PLUS_EXPR, there
+     is nothing to do. */
+  if (TREE_CODE (rhs) != POINTER_PLUS_EXPR)
+    return false;
+
+  /* Try to optimize &x[0] p+ C where C is a multiple of the size
+     of the elements in X into &x[C/element size].  */
+  if (TREE_OPERAND (rhs, 0) == name
+      && TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
+    {
+      tree orig = unshare_expr (rhs);
+      TREE_OPERAND (rhs, 0) = unshare_expr (def_rhs);
+
+      /* If folding succeeds, then we have just exposed new variables
+        in USE_STMT which will need to be renamed.  If folding fails,
+        then we need to put everything back the way it was.  */
+      if (fold_stmt_inplace (use_stmt))

        {
        {

-         tree cond = COND_EXPR_COND (last);
-         enum tree_code cond_code = TREE_CODE (cond);
-
-         /* If the condition is a lone variable or an equality test of
-            an SSA_NAME against an integral constant, then we may have an 
-            optimizable case.
-
-            Note these conditions also ensure the COND_EXPR has no
-            virtual operands or other side effects.  */
-         if (cond_code == SSA_NAME
-             || ((cond_code == EQ_EXPR || cond_code == NE_EXPR)
-                 && TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME
-                 && CONSTANT_CLASS_P (TREE_OPERAND (cond, 1))
-                 && INTEGRAL_TYPE_P (TREE_TYPE (TREE_OPERAND (cond, 1)))))
-           {
-             tree def;
-             tree test_var;
+         tidy_after_forward_propagate_addr (use_stmt);
+         return true;
+       }
+      else
+       {
+         GIMPLE_STMT_OPERAND (use_stmt, 1) = orig;
+         update_stmt (use_stmt);
+         return false;
+       }
+    }

 
 

-             /* Extract the single variable used in the test into TEST_VAR.  */
-             if (cond_code == SSA_NAME)
-               test_var = cond;
-             else
-               test_var = TREE_OPERAND (cond, 0);
+  /* Try to optimize &x[0] p+ OFFSET where OFFSET is defined by
+     converting a multiplication of an index by the size of the
+     array elements, then the result is converted into the proper
+     type for the arithmetic.  */
+  if (TREE_OPERAND (rhs, 0) == name
+      && TREE_CODE (TREE_OPERAND (rhs, 1)) == SSA_NAME
+      /* Avoid problems with IVopts creating PLUS_EXPRs with a
+        different type than their operands.  */
+      && useless_type_conversion_p (TREE_TYPE (rhs), TREE_TYPE (name)))
+    {
+      bool res;
+      
+      res = forward_propagate_addr_into_variable_array_index (TREE_OPERAND (rhs, 1),
+                                                             def_rhs, use_stmt);
+      return res;
+    }
+  return false;
+}

 
 

-             /* If we have already recorded this SSA_NAME as interesting,
-                do not do so again.  */
-             if (bitmap_bit_p (vars, SSA_NAME_VERSION (test_var)))
-               continue;
+/* STMT is a statement of the form SSA_NAME = ADDR_EXPR <whatever>.

 
 

-             /* Now get the defining statement for TEST_VAR and see if it
-                something we are interested in.  */
-             def = SSA_NAME_DEF_STMT (test_var);
-             if (TREE_CODE (def) == MODIFY_EXPR)
-               {
-                 tree def_rhs = TREE_OPERAND (def, 1);
-
-                 /* If TEST_VAR is set by adding or subtracting a constant
-                    from an SSA_NAME, then it is interesting to us as we
-                    can adjust the constant in the conditional and thus
-                    eliminate the arithmetic operation.  */
-                 if (TREE_CODE (def_rhs) == PLUS_EXPR
-                        || TREE_CODE (def_rhs) == MINUS_EXPR)
-                   {
-                     tree op0 = TREE_OPERAND (def_rhs, 0);
-                     tree op1 = TREE_OPERAND (def_rhs, 1);
-
-                     /* The first operand must be an SSA_NAME and the second
-                        operand must be a constant.  */
-                     if (TREE_CODE (op0) != SSA_NAME
-                         || !CONSTANT_CLASS_P (op1)
-                         || !INTEGRAL_TYPE_P (TREE_TYPE (op1)))
-                       continue;
-                     
-                     /* Don't propagate if the first operand occurs in
-                        an abnormal PHI.  */
-                     if (SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0))
-                       continue;
-                   }
+   Try to forward propagate the ADDR_EXPR into all uses of the SSA_NAME.
+   Often this will allow for removal of an ADDR_EXPR and INDIRECT_REF
+   node or for recovery of array indexing from pointer arithmetic.
+   Returns true, if all uses have been propagated into.  */

 
 

-                 /* These cases require comparisons of a naked SSA_NAME or
-                    comparison of an SSA_NAME against zero or one.  */
-                 else if (TREE_CODE (cond) == SSA_NAME
-                          || integer_zerop (TREE_OPERAND (cond, 1))
-                          || integer_onep (TREE_OPERAND (cond, 1)))
-                   {
-                     /* If TEST_VAR is set from a relational operation
-                        between two SSA_NAMEs or a combination of an SSA_NAME
-                        and a constant, then it is interesting.  */
-                     if (COMPARISON_CLASS_P (def_rhs))
-                       {
-                         tree op0 = TREE_OPERAND (def_rhs, 0);
-                         tree op1 = TREE_OPERAND (def_rhs, 1);
-
-                         /* Both operands of DEF_RHS must be SSA_NAMEs or
-                            constants.  */
-                         if ((TREE_CODE (op0) != SSA_NAME
-                              && !is_gimple_min_invariant (op0))
-                             || (TREE_CODE (op1) != SSA_NAME
-                                 && !is_gimple_min_invariant (op1)))
-                           continue;
-                     
-                         /* Don't propagate if the first operand occurs in
-                            an abnormal PHI.  */
-                         if (TREE_CODE (op0) == SSA_NAME
-                             && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op0))
-                           continue;
-                     
-                         /* Don't propagate if the second operand occurs in
-                            an abnormal PHI.  */
-                         if (TREE_CODE (op1) == SSA_NAME
-                             && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (op1))
-                           continue;
-                       }
-
-                     /* If TEST_VAR is set from a TRUTH_NOT_EXPR, then it
-                        is interesting.  */
-                     else if (TREE_CODE (def_rhs) == TRUTH_NOT_EXPR)
-                       {
-                         def_rhs = TREE_OPERAND (def_rhs, 0);
-
-                         /* DEF_RHS must be an SSA_NAME or constant.  */
-                         if (TREE_CODE (def_rhs) != SSA_NAME
-                             && !is_gimple_min_invariant (def_rhs))
-                           continue;
-                     
-                         /* Don't propagate if the operand occurs in
-                            an abnormal PHI.  */
-                         if (TREE_CODE (def_rhs) == SSA_NAME
-                             && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (def_rhs))
-                           continue;
-                       }
-
-                     /* If TEST_VAR was set from a cast of an integer type
-                        to a boolean type or a cast of a boolean to an
-                        integral, then it is interesting.  */
-                     else if (TREE_CODE (def_rhs) == NOP_EXPR
-                              || TREE_CODE (def_rhs) == CONVERT_EXPR)
-                       {
-                         tree outer_type;
-                         tree inner_type;
-
-                         outer_type = TREE_TYPE (def_rhs);
-                         inner_type = TREE_TYPE (TREE_OPERAND (def_rhs, 0));
-
-                         if ((TREE_CODE (outer_type) == BOOLEAN_TYPE
-                              && INTEGRAL_TYPE_P (inner_type))
-                             || (TREE_CODE (inner_type) == BOOLEAN_TYPE
-                                 && INTEGRAL_TYPE_P (outer_type)))
-                           ;
-                         else
-                           continue;
-                     
-                         /* Don't propagate if the operand occurs in
-                            an abnormal PHI.  */
-                         if (TREE_CODE (TREE_OPERAND (def_rhs, 0)) == SSA_NAME
-                             && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND
-                                                                 (def_rhs, 0)))
-                           continue;
-                       }
-                     else
-                       continue;
-                   }
-                 else
-                   continue;
+static bool
+forward_propagate_addr_expr (tree name, tree rhs)
+{
+  int stmt_loop_depth = bb_for_stmt (SSA_NAME_DEF_STMT (name))->loop_depth;
+  imm_use_iterator iter;
+  tree use_stmt;
+  bool all = true;
+  bool single_use_p = has_single_use (name);

 
 

-                 /* All the tests passed, record TEST_VAR as interesting.  */
-                 VARRAY_PUSH_TREE (*vars_worklist, test_var);
-                 bitmap_set_bit (vars, SSA_NAME_VERSION (test_var));
-               }
-           }
+  FOR_EACH_IMM_USE_STMT (use_stmt, iter, name)
+    {
+      bool result;
+
+      /* If the use is not in a simple assignment statement, then
+        there is nothing we can do.  */
+      if (TREE_CODE (use_stmt) != GIMPLE_MODIFY_STMT)
+       {
+         all = false;
+         continue;
+       }
+
+      /* If the use is in a deeper loop nest, then we do not want
+       to propagate the ADDR_EXPR into the loop as that is likely
+       adding expression evaluations into the loop.  */
+      if (bb_for_stmt (use_stmt)->loop_depth > stmt_loop_depth)
+       {
+         all = false;
+         continue;
+       }
+
+      /* If the use_stmt has side-effects, don't propagate into it.  */
+      if (stmt_ann (use_stmt)->has_volatile_ops)
+       {
+         all = false;
+         continue;
+       }
+
+      push_stmt_changes (&use_stmt);
+
+      result = forward_propagate_addr_expr_1 (name, rhs, use_stmt,
+                                             single_use_p);
+      all &= result;
+
+      pop_stmt_changes (&use_stmt);
+
+      /* Remove intermediate now unused copy and conversion chains.  */
+      if (result
+         && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME
+         && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == SSA_NAME
+             || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == NOP_EXPR
+             || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == CONVERT_EXPR))
+       {
+         block_stmt_iterator bsi = bsi_for_stmt (use_stmt);
+         release_defs (use_stmt);
+         bsi_remove (&bsi, true);

        }
     }
        }
     }

+
+  return all;

 }
 
 }
 

-/* Given FORWPROP_DATA containing SSA_NAMEs which are used in COND_EXPRs
-   that we may be able to optimize, attempt to rewrite the condition
-   in each COND_EXPR to use the RHS of the statement which defines the
-   SSA_NAME used in the COND_EXPR.  */
-  
-static void
-substitute_single_use_vars (varray_type *cond_worklist,
-                           varray_type vars_worklist)
+/* Forward propagate the comparison COND defined in STMT like
+   cond_1 = x CMP y to uses of the form
+     a_1 = (T')cond_1
+     a_1 = !cond_1
+     a_1 = cond_1 != 0
+   Returns true if stmt is now unused.  */
+
+static bool
+forward_propagate_comparison (tree cond, tree stmt)

 {
 {

-  while (VARRAY_ACTIVE_SIZE (vars_worklist) > 0)
+  tree name = GIMPLE_STMT_OPERAND (stmt, 0);
+  tree use_stmt, tmp = NULL_TREE;
+
+  /* Don't propagate ssa names that occur in abnormal phis.  */
+  if ((TREE_CODE (TREE_OPERAND (cond, 0)) == SSA_NAME
+       && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 0)))
+      || (TREE_CODE (TREE_OPERAND (cond, 1)) == SSA_NAME
+         && SSA_NAME_OCCURS_IN_ABNORMAL_PHI (TREE_OPERAND (cond, 1))))
+    return false;
+
+  /* Do not un-cse comparisons.  But propagate through copies.  */
+  use_stmt = get_prop_dest_stmt (name, &name);
+  if (use_stmt == NULL_TREE)
+    return false;
+
+  /* Conversion of the condition result to another integral type.  */
+  if (TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
+      && (TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == CONVERT_EXPR
+         || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == NOP_EXPR
+          || COMPARISON_CLASS_P (GIMPLE_STMT_OPERAND (use_stmt, 1))
+          || TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == TRUTH_NOT_EXPR)
+      && INTEGRAL_TYPE_P (TREE_TYPE (GIMPLE_STMT_OPERAND (use_stmt, 0))))

     {
     {

-      tree test_var = VARRAY_TOP_TREE (vars_worklist);
-      tree def = SSA_NAME_DEF_STMT (test_var);
-      dataflow_t df;
-      int j, num_uses, propagated_uses;
-      block_stmt_iterator bsi;
+      tree lhs = GIMPLE_STMT_OPERAND (use_stmt, 0);
+      tree rhs = GIMPLE_STMT_OPERAND (use_stmt, 1);

 
 

-      VARRAY_POP (vars_worklist);
-
-      /* Now compute the immediate uses of TEST_VAR.  */
-      df = get_immediate_uses (def);
-      num_uses = num_immediate_uses (df);
-      propagated_uses = 0;
-
-      /* If TEST_VAR is used more than once and is not a boolean set
-        via TRUTH_NOT_EXPR with another SSA_NAME as its argument, then
-        we can not optimize.  */
-      if (num_uses == 1
-         || (TREE_CODE (TREE_TYPE (test_var)) == BOOLEAN_TYPE
-             && TREE_CODE (TREE_OPERAND (def, 1)) == TRUTH_NOT_EXPR
-             && (TREE_CODE (TREE_OPERAND (TREE_OPERAND (def, 1), 0))
-                 == SSA_NAME)))
-       ;
+      /* We can propagate the condition into a conversion.  */
+      if (TREE_CODE (rhs) == CONVERT_EXPR
+         || TREE_CODE (rhs) == NOP_EXPR)
+       {
+         /* Avoid using fold here as that may create a COND_EXPR with
+            non-boolean condition as canonical form.  */
+         tmp = build2 (TREE_CODE (cond), TREE_TYPE (lhs),
+                       TREE_OPERAND (cond, 0), TREE_OPERAND (cond, 1));
+       }
+      /* We can propagate the condition into X op CST where op
+        is EQ_EXRP or NE_EXPR and CST is either one or zero.  */
+      else if (COMPARISON_CLASS_P (rhs)
+              && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME
+              && TREE_CODE (TREE_OPERAND (rhs, 1)) == INTEGER_CST)
+       {
+         enum tree_code code = TREE_CODE (rhs);
+         tree cst = TREE_OPERAND (rhs, 1);
+
+         tmp = combine_cond_expr_cond (code, TREE_TYPE (lhs),
+                                       fold_convert (TREE_TYPE (cst), cond),
+                                       cst, false);
+         if (tmp == NULL_TREE)
+           return false;
+       }
+      /* We can propagate the condition into a statement that
+        computes the logical negation of the comparison result.  */
+      else if (TREE_CODE (rhs) == TRUTH_NOT_EXPR)
+       {
+         tree type = TREE_TYPE (TREE_OPERAND (cond, 0));
+         bool nans = HONOR_NANS (TYPE_MODE (type));
+         enum tree_code code;
+         code = invert_tree_comparison (TREE_CODE (cond), nans);
+         if (code == ERROR_MARK)
+           return false;
+
+         tmp = build2 (code, TREE_TYPE (lhs), TREE_OPERAND (cond, 0),
+                       TREE_OPERAND (cond, 1));
+       }

       else
       else

-       continue;
+       return false;
+
+      GIMPLE_STMT_OPERAND (use_stmt, 1) = unshare_expr (tmp);
+      update_stmt (use_stmt);
+
+      /* Remove defining statements.  */
+      remove_prop_source_from_use (name, stmt);
+
+      if (dump_file && (dump_flags & TDF_DETAILS))
+       {
+         fprintf (dump_file, "  Replaced '");
+         print_generic_expr (dump_file, rhs, dump_flags);
+         fprintf (dump_file, "' with '");
+         print_generic_expr (dump_file, tmp, dump_flags);
+         fprintf (dump_file, "'\n");
+       }
+
+      return true;
+    }
+
+  return false;
+}
+
+/* If we have lhs = ~x (STMT), look and see if earlier we had x = ~y.
+   If so, we can change STMT into lhs = y which can later be copy
+   propagated.  Similarly for negation. 
+
+   This could trivially be formulated as a forward propagation 
+   to immediate uses.  However, we already had an implementation
+   from DOM which used backward propagation via the use-def links.
+
+   It turns out that backward propagation is actually faster as
+   there's less work to do for each NOT/NEG expression we find.
+   Backwards propagation needs to look at the statement in a single
+   backlink.  Forward propagation needs to look at potentially more
+   than one forward link.  */
+
+static void
+simplify_not_neg_expr (tree stmt)
+{
+  tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);
+  tree rhs_def_stmt = SSA_NAME_DEF_STMT (TREE_OPERAND (rhs, 0));
+
+  /* See if the RHS_DEF_STMT has the same form as our statement.  */
+  if (TREE_CODE (rhs_def_stmt) == GIMPLE_MODIFY_STMT
+      && TREE_CODE (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1)) == TREE_CODE (rhs))
+    {
+      tree rhs_def_operand =
+       TREE_OPERAND (GIMPLE_STMT_OPERAND (rhs_def_stmt, 1), 0);

 
 

-      /* Walk over each use and try to forward propagate the RHS of
-        DEF into the use.  */
-      for (j = 0; j < num_uses; j++)
+      /* Verify that RHS_DEF_OPERAND is a suitable SSA_NAME.  */
+      if (TREE_CODE (rhs_def_operand) == SSA_NAME
+         && ! SSA_NAME_OCCURS_IN_ABNORMAL_PHI (rhs_def_operand))

        {
        {

-         tree cond_stmt;
-         tree cond;
-         enum tree_code cond_code;
-         tree def_rhs;
-         enum tree_code def_rhs_code;
-         tree new_cond;
-
-         cond_stmt = immediate_use (df, j);
-
-         /* For now we can only propagate into COND_EXPRs.  */
-         if (TREE_CODE (cond_stmt) != COND_EXPR) 
-           continue;
-
-         cond = COND_EXPR_COND (cond_stmt);
-         cond_code = TREE_CODE (cond);
-         def_rhs = TREE_OPERAND (def, 1);
-         def_rhs_code = TREE_CODE (def_rhs);
-
-         /* If the definition of the single use variable was from an
-            arithmetic operation, then we just need to adjust the
-            constant in the COND_EXPR_COND and update the variable tested.  */
-         if (def_rhs_code == PLUS_EXPR || def_rhs_code == MINUS_EXPR)
+         GIMPLE_STMT_OPERAND (stmt, 1) = rhs_def_operand;
+         update_stmt (stmt);
+       }
+    }
+}
+
+/* STMT is a SWITCH_EXPR for which we attempt to find equivalent forms of
+   the condition which we may be able to optimize better.  */
+
+static void
+simplify_switch_expr (tree stmt)
+{
+  tree cond = SWITCH_COND (stmt);
+  tree def, to, ti;
+
+  /* The optimization that we really care about is removing unnecessary
+     casts.  That will let us do much better in propagating the inferred
+     constant at the switch target.  */
+  if (TREE_CODE (cond) == SSA_NAME)
+    {
+      def = SSA_NAME_DEF_STMT (cond);
+      if (TREE_CODE (def) == GIMPLE_MODIFY_STMT)
+       {
+         def = GIMPLE_STMT_OPERAND (def, 1);
+         if (TREE_CODE (def) == NOP_EXPR)

            {
            {

-             tree op0 = TREE_OPERAND (def_rhs, 0);
-             tree op1 = TREE_OPERAND (def_rhs, 1);
-             enum tree_code new_code;
-             tree t;
-
-             /* If the variable was defined via X + C, then we must subtract
-                C from the constant in the conditional.  Otherwise we add
-                C to the constant in the conditional.  The result must fold
-                into a valid gimple operand to be optimizable.  */
-             new_code = def_rhs_code == PLUS_EXPR ? MINUS_EXPR : PLUS_EXPR;
-             t = int_const_binop (new_code, TREE_OPERAND (cond, 1), op1, 0);
-             if (!is_gimple_val (t))
-               continue;
-
-             new_cond = build (cond_code, boolean_type_node, op0, t);
+             int need_precision;
+             bool fail;
+
+             def = TREE_OPERAND (def, 0);
+
+#ifdef ENABLE_CHECKING
+             /* ??? Why was Jeff testing this?  We are gimple...  */
+             gcc_assert (is_gimple_val (def));
+#endif
+
+             to = TREE_TYPE (cond);
+             ti = TREE_TYPE (def);
+
+             /* If we have an extension that preserves value, then we
+                can copy the source value into the switch.  */
+
+             need_precision = TYPE_PRECISION (ti);
+             fail = false;
+             if (! INTEGRAL_TYPE_P (ti))
+               fail = true;
+             else if (TYPE_UNSIGNED (to) && !TYPE_UNSIGNED (ti))
+               fail = true;
+             else if (!TYPE_UNSIGNED (to) && TYPE_UNSIGNED (ti))
+               need_precision += 1;
+             if (TYPE_PRECISION (to) < need_precision)
+               fail = true;
+
+             if (!fail)
+               {
+                 SWITCH_COND (stmt) = def;
+                 update_stmt (stmt);
+               }

            }
            }

-         /* If the variable is defined by a conditional expression... */
-         else if (TREE_CODE_CLASS (def_rhs_code) == tcc_comparison)
+       }
+    }
+}
+
+/* Main entry point for the forward propagation optimizer.  */
+
+static unsigned int
+tree_ssa_forward_propagate_single_use_vars (void)
+{
+  basic_block bb;
+  unsigned int todoflags = 0;
+
+  cfg_changed = false;
+
+  FOR_EACH_BB (bb)
+    {
+      block_stmt_iterator bsi;
+
+      /* Note we update BSI within the loop as necessary.  */
+      for (bsi = bsi_start (bb); !bsi_end_p (bsi); )
+       {
+         tree stmt = bsi_stmt (bsi);
+
+         /* If this statement sets an SSA_NAME to an address,
+            try to propagate the address into the uses of the SSA_NAME.  */
+         if (TREE_CODE (stmt) == GIMPLE_MODIFY_STMT)

            {
            {

-             /* TEST_VAR was set from a relational operator.  */
-             tree op0 = TREE_OPERAND (def_rhs, 0);
-             tree op1 = TREE_OPERAND (def_rhs, 1);
+             tree lhs = GIMPLE_STMT_OPERAND (stmt, 0);
+             tree rhs = GIMPLE_STMT_OPERAND (stmt, 1);

 
 

-             new_cond = build (def_rhs_code, boolean_type_node, op0, op1);

 
 

-             /* Invert the conditional if necessary.  */
-             if ((cond_code == EQ_EXPR
-                  && integer_zerop (TREE_OPERAND (cond, 1)))
-                 || (cond_code == NE_EXPR
-                     && integer_onep (TREE_OPERAND (cond, 1))))
+             if (TREE_CODE (lhs) != SSA_NAME)

                {
                {

-                 new_cond = invert_truthvalue (new_cond);
+                 bsi_next (&bsi);
+                 continue;
+               }

 
 

-                 /* If we did not get a simple relational expression or
-                    bare SSA_NAME, then we can not optimize this case.  */
-                 if (!COMPARISON_CLASS_P (new_cond)
-                     && TREE_CODE (new_cond) != SSA_NAME)
-                   continue;
+             if (TREE_CODE (rhs) == ADDR_EXPR)
+               {
+                 if (forward_propagate_addr_expr (lhs, rhs))
+                   {
+                     release_defs (stmt);
+                     todoflags |= TODO_remove_unused_locals;
+                     bsi_remove (&bsi, true);
+                   }
+                 else
+                   bsi_next (&bsi);
+               }
+             else if ((TREE_CODE (rhs) == BIT_NOT_EXPR
+                       || TREE_CODE (rhs) == NEGATE_EXPR)
+                      && TREE_CODE (TREE_OPERAND (rhs, 0)) == SSA_NAME)
+               {
+                 simplify_not_neg_expr (stmt);
+                 bsi_next (&bsi);

                }
                }

+              else if (TREE_CODE (rhs) == COND_EXPR)
+                {
+                 int did_something;
+                 fold_defer_overflow_warnings ();
+                  did_something = forward_propagate_into_cond (rhs, stmt);
+                 if (did_something == 2)
+                   cfg_changed = true;
+                 fold_undefer_overflow_warnings (!TREE_NO_WARNING (rhs)
+                   && did_something, stmt, WARN_STRICT_OVERFLOW_CONDITIONAL);
+                 bsi_next (&bsi);
+                }
+             else if (COMPARISON_CLASS_P (rhs))
+               {
+                 if (forward_propagate_comparison (rhs, stmt))
+                   {
+                     release_defs (stmt);
+                     todoflags |= TODO_remove_unused_locals;
+                     bsi_remove (&bsi, true);
+                   }
+                 else
+                   bsi_next (&bsi);
+               }
+             else
+               bsi_next (&bsi);

            }
            }

-         else
+         else if (TREE_CODE (stmt) == SWITCH_EXPR)

            {
            {

-             bool invert = false;
-             enum tree_code new_code;
-             tree new_arg;
-
-             /* TEST_VAR was set from a TRUTH_NOT_EXPR or a NOP_EXPR.  */
-             if (def_rhs_code == TRUTH_NOT_EXPR)
-               invert = true;
-               
-             if (cond_code == SSA_NAME
-                 || (cond_code == NE_EXPR
-                     && integer_zerop (TREE_OPERAND (cond, 1)))
-                 || (cond_code == EQ_EXPR
-                     && integer_onep (TREE_OPERAND (cond, 1))))
-               new_code = NE_EXPR;
-             else
-               new_code = EQ_EXPR;
+             simplify_switch_expr (stmt);
+             bsi_next (&bsi);
+           }
+         else if (TREE_CODE (stmt) == COND_EXPR)
+           {
+             int did_something;
+             fold_defer_overflow_warnings ();
+             did_something = forward_propagate_into_cond (stmt, stmt);
+             if (did_something == 2)
+               cfg_changed = true;
+             fold_undefer_overflow_warnings (!TREE_NO_WARNING (stmt)
+                                             && did_something, stmt,
+                                             WARN_STRICT_OVERFLOW_CONDITIONAL);
+             bsi_next (&bsi);
+           }
+         else
+           bsi_next (&bsi);
+       }
+    }

 
 

-             if (invert)
-               new_code = (new_code == EQ_EXPR ? NE_EXPR  : EQ_EXPR);
+  if (cfg_changed)
+    todoflags |= TODO_cleanup_cfg;
+  return todoflags;
+}

 
 

-             new_arg = TREE_OPERAND (def_rhs, 0);
-             new_cond = build2 (new_code, boolean_type_node, new_arg,
-                                fold_convert (TREE_TYPE (new_arg),
-                                              integer_zero_node));
-           }

 
 

-         /* Dump details.  */
-         if (dump_file && (dump_flags & TDF_DETAILS))
+static bool
+gate_forwprop (void)
+{
+  return 1;
+}
+
+struct tree_opt_pass pass_forwprop = {
+  "forwprop",                  /* name */
+  gate_forwprop,               /* gate */
+  tree_ssa_forward_propagate_single_use_vars,  /* execute */
+  NULL,                                /* sub */
+  NULL,                                /* next */
+  0,                           /* static_pass_number */
+  TV_TREE_FORWPROP,            /* tv_id */
+  PROP_cfg | PROP_ssa,         /* properties_required */
+  0,                           /* properties_provided */
+  0,                           /* properties_destroyed */
+  0,                           /* todo_flags_start */
+  TODO_dump_func
+  | TODO_ggc_collect
+  | TODO_update_ssa
+  | TODO_verify_ssa,           /* todo_flags_finish */
+  0                            /* letter */
+};
+
+
+/* Structure to keep track of the value of a dereferenced PHI result
+   and the set of virtual operands used for that dereference.  */
+
+struct phiprop_d
+{
+  tree value;
+  tree vop_stmt;
+};
+
+/* Verify if the value recorded for NAME in PHIVN is still valid at
+   the start of basic block BB.  */
+
+static bool
+phivn_valid_p (struct phiprop_d *phivn, tree name, basic_block bb)
+{
+  tree vop_stmt = phivn[SSA_NAME_VERSION (name)].vop_stmt;
+  ssa_op_iter ui;
+  tree vuse;
+
+  /* The def stmts of all virtual uses need to be post-dominated
+     by bb.  */
+  FOR_EACH_SSA_TREE_OPERAND (vuse, vop_stmt, ui, SSA_OP_VUSE)
+    {
+      tree use_stmt;
+      imm_use_iterator ui2;
+      bool ok = true;
+
+      FOR_EACH_IMM_USE_STMT (use_stmt, ui2, vuse)
+       {
+         /* If BB does not dominate a VDEF, the value is invalid.  */
+         if (((TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
+               && !ZERO_SSA_OPERANDS (use_stmt, SSA_OP_VDEF))
+              || TREE_CODE (use_stmt) == PHI_NODE)
+             && !dominated_by_p (CDI_DOMINATORS, bb_for_stmt (use_stmt), bb))

            {
            {

-             fprintf (dump_file, "  Replaced '");
-             print_generic_expr (dump_file, cond, dump_flags);
-             fprintf (dump_file, "' with '");
-             print_generic_expr (dump_file, new_cond, dump_flags);
-             fprintf (dump_file, "'\n");
+             ok = false;
+             BREAK_FROM_IMM_USE_STMT (ui2);

            }
            }

-
-         /* Replace the condition.  */
-         COND_EXPR_COND (cond_stmt) = new_cond;
-         modify_stmt (cond_stmt);
-         propagated_uses++;
-         VARRAY_PUSH_TREE (*cond_worklist, cond_stmt);

        }
        }

-
-      /* If we propagated into all the uses, then we can delete DEF.
-        Unfortunately, we have to find the defining statement in
-        whatever block it might be in.  */
-      if (num_uses && num_uses == propagated_uses)
-       for (bsi = bsi_start (bb_for_stmt (def));
-            !bsi_end_p (bsi);
-            bsi_next (&bsi))
-         {
-           if (def == bsi_stmt (bsi))
-             {
-               bsi_remove (&bsi);
-               break;
-             }
-         }
+      if (!ok)
+       return false;

     }
     }

+
+  return true;

 }
 
 }
 

-/* Main entry point for the forward propagation optimizer.  */
+/* Insert a new phi node for the dereference of PHI at basic_block
+   BB with the virtual operands from USE_STMT.  */

 
 

-static void
-tree_ssa_forward_propagate_single_use_vars (void)
+static tree
+phiprop_insert_phi (basic_block bb, tree phi, tree use_stmt,
+                   struct phiprop_d *phivn, size_t n)

 {
 {

-  basic_block bb;
-  varray_type vars_worklist, cond_worklist;
+  tree res, new_phi;
+  edge_iterator ei;
+  edge e;
+
+  /* Build a new PHI node to replace the definition of
+     the indirect reference lhs.  */
+  res = GIMPLE_STMT_OPERAND (use_stmt, 0);
+  SSA_NAME_DEF_STMT (res) = new_phi = create_phi_node (res, bb);
+
+  /* Add PHI arguments for each edge inserting loads of the
+     addressable operands.  */
+  FOR_EACH_EDGE (e, ei, bb->preds)
+    {
+      tree old_arg, new_var, tmp;

 
 

-  vars = BITMAP_XMALLOC ();
-  VARRAY_TREE_INIT (vars_worklist, 10, "VARS worklist");
-  VARRAY_TREE_INIT (cond_worklist, 10, "COND worklist");
+      old_arg = PHI_ARG_DEF_FROM_EDGE (phi, e);
+      while (TREE_CODE (old_arg) == SSA_NAME
+            && (SSA_NAME_VERSION (old_arg) >= n
+                || phivn[SSA_NAME_VERSION (old_arg)].value == NULL_TREE))
+       {
+         tree def_stmt = SSA_NAME_DEF_STMT (old_arg);
+         old_arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
+       }

 
 

-  /* Prime the COND_EXPR worklist by placing all the COND_EXPRs on the
-     worklist.  */
-  FOR_EACH_BB (bb)
+      if (TREE_CODE (old_arg) == SSA_NAME)
+       /* Reuse a formerly created dereference.  */
+       new_var = phivn[SSA_NAME_VERSION (old_arg)].value;
+      else
+       {
+         old_arg = TREE_OPERAND (old_arg, 0);
+         new_var = create_tmp_var (TREE_TYPE (old_arg), NULL);
+         tmp = build2 (GIMPLE_MODIFY_STMT, void_type_node,
+                       NULL_TREE, unshare_expr (old_arg));
+         if (TREE_CODE (TREE_TYPE (old_arg)) == COMPLEX_TYPE
+             || TREE_CODE (TREE_TYPE (old_arg)) == VECTOR_TYPE)
+           DECL_GIMPLE_REG_P (new_var) = 1;
+         add_referenced_var (new_var);
+         new_var = make_ssa_name (new_var, tmp);
+         GIMPLE_STMT_OPERAND (tmp, 0) = new_var;
+
+         bsi_insert_on_edge (e, tmp);
+
+         update_stmt (tmp);
+         mark_symbols_for_renaming (tmp);
+       }
+
+      add_phi_arg (new_phi, new_var, e);
+    }
+
+  update_stmt (new_phi);
+
+  return res;
+}
+
+/* Propagate between the phi node arguments of PHI in BB and phi result
+   users.  For now this matches
+        # p_2 = PHI <&x, &y>
+      <Lx>:;
+       p_3 = p_2;
+       z_2 = *p_3;
+   and converts it to
+       # z_2 = PHI <x, y>
+      <Lx>:;
+   Returns true if a transformation was done and edge insertions
+   need to be committed.  Global data PHIVN and N is used to track
+   past transformation results.  We need to be especially careful here
+   with aliasing issues as we are moving memory reads.  */
+
+static bool
+propagate_with_phi (basic_block bb, tree phi, struct phiprop_d *phivn, size_t n)
+{
+  tree ptr = PHI_RESULT (phi);
+  tree use_stmt, res = NULL_TREE;
+  block_stmt_iterator bsi;
+  imm_use_iterator ui;
+  use_operand_p arg_p, use;
+  ssa_op_iter i;
+  bool phi_inserted;
+
+  if (MTAG_P (SSA_NAME_VAR (ptr))
+      || !POINTER_TYPE_P (TREE_TYPE (ptr))
+      || !is_gimple_reg_type (TREE_TYPE (TREE_TYPE (ptr))))
+    return false;
+
+  /* Check if we can "cheaply" dereference all phi arguments.  */
+  FOR_EACH_PHI_ARG (arg_p, phi, i, SSA_OP_USE)

     {
     {

-      tree last = last_stmt (bb);
-      if (last && TREE_CODE (last) == COND_EXPR)
-       VARRAY_PUSH_TREE (cond_worklist, last);
+      tree arg = USE_FROM_PTR (arg_p);
+      /* Walk the ssa chain until we reach a ssa name we already
+        created a value for or we reach a definition of the form
+        ssa_name_n = &var;  */
+      while (TREE_CODE (arg) == SSA_NAME
+            && !SSA_NAME_IS_DEFAULT_DEF (arg)
+            && (SSA_NAME_VERSION (arg) >= n
+                || phivn[SSA_NAME_VERSION (arg)].value == NULL_TREE))
+       {
+         tree def_stmt = SSA_NAME_DEF_STMT (arg);
+         if (TREE_CODE (def_stmt) != GIMPLE_MODIFY_STMT)
+           return false;
+         arg = GIMPLE_STMT_OPERAND (def_stmt, 1);
+       }
+      if ((TREE_CODE (arg) != ADDR_EXPR
+          /* Avoid to have to decay *&a to a[0] later.  */
+          || !is_gimple_reg_type (TREE_TYPE (TREE_OPERAND (arg, 0))))
+         && !(TREE_CODE (arg) == SSA_NAME
+              && phivn[SSA_NAME_VERSION (arg)].value != NULL_TREE
+              && phivn_valid_p (phivn, arg, bb)))
+       return false;

     }
 
     }
 

-  while (VARRAY_ACTIVE_SIZE (cond_worklist) > 0)
+  /* Find a dereferencing use.  First follow (single use) ssa
+     copy chains for ptr.  */
+  while (single_imm_use (ptr, &use, &use_stmt)
+        && TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
+        && GIMPLE_STMT_OPERAND (use_stmt, 1) == ptr
+        && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME)
+    ptr = GIMPLE_STMT_OPERAND (use_stmt, 0);
+
+  /* Replace the first dereference of *ptr if there is one and if we
+     can move the loads to the place of the ptr phi node.  */
+  phi_inserted = false;
+  FOR_EACH_IMM_USE_STMT (use_stmt, ui, ptr)

     {
     {

-      /* First get a list of all the interesting COND_EXPRs and potential
-        single use variables which feed those COND_EXPRs.  This will drain
-        COND_WORKLIST and initialize VARS_WORKLIST.  */
-      record_single_argument_cond_exprs (cond_worklist, &vars_worklist, vars);
+      ssa_op_iter ui2;
+      tree vuse;
+
+      /* Check whether this is a load of *ptr.  */
+      if (!(TREE_CODE (use_stmt) == GIMPLE_MODIFY_STMT
+           && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 0)) == SSA_NAME 
+           && TREE_CODE (GIMPLE_STMT_OPERAND (use_stmt, 1)) == INDIRECT_REF
+           && TREE_OPERAND (GIMPLE_STMT_OPERAND (use_stmt, 1), 0) == ptr
+           /* We cannot replace a load that may throw or is volatile.  */
+           && !tree_can_throw_internal (use_stmt)))
+       continue;

 
 

-      if (VARRAY_ACTIVE_SIZE (vars_worklist) > 0)
+      /* Check if we can move the loads.  The def stmts of all virtual uses
+        need to be post-dominated by bb.  */
+      FOR_EACH_SSA_TREE_OPERAND (vuse, use_stmt, ui2, SSA_OP_VUSE)

        {
        {

-         /* Now compute immediate uses for all the variables we care about.  */
-         compute_immediate_uses (TDFA_USE_OPS, need_imm_uses_for);
-
-         /* We've computed immediate uses, so we can/must clear the VARS
-            bitmap for the next iteration.  */
-         bitmap_clear (vars);
-
-         /* And optimize.  This will drain VARS_WORKLIST and initialize
-            COND_WORKLIST for the next iteration.  */
-         substitute_single_use_vars (&cond_worklist, vars_worklist);
-
-         /* We do not incrementally update the dataflow information
-            so we must free it here and recompute the necessary bits
-            on the next iteration.  If this turns out to be expensive,
-            methods for incrementally updating the dataflow are known.  */
-         free_df ();
+         tree def_stmt = SSA_NAME_DEF_STMT (vuse);
+         if (!SSA_NAME_IS_DEFAULT_DEF (vuse)
+             && (bb_for_stmt (def_stmt) == bb
+                 || !dominated_by_p (CDI_DOMINATORS,
+                                     bb, bb_for_stmt (def_stmt))))
+           goto next;

        }
        }

+
+      /* Found a proper dereference.  Insert a phi node if this
+        is the first load transformation.  */
+      if (!phi_inserted)
+       {
+         res = phiprop_insert_phi (bb, phi, use_stmt, phivn, n);
+
+         /* Remember the value we created for *ptr.  */
+         phivn[SSA_NAME_VERSION (ptr)].value = res;
+         phivn[SSA_NAME_VERSION (ptr)].vop_stmt = use_stmt;
+
+         /* Remove old stmt.  The phi is taken care of by DCE, if we
+            want to delete it here we also have to delete all intermediate
+            copies.  */
+         bsi = bsi_for_stmt (use_stmt);
+         bsi_remove (&bsi, 0);
+
+         phi_inserted = true;
+       }
+      else
+       {
+         /* Further replacements are easy, just make a copy out of the
+            load.  */
+         GIMPLE_STMT_OPERAND (use_stmt, 1) = res;
+         update_stmt (use_stmt);
+       }
+
+next:;
+      /* Continue searching for a proper dereference.  */

     }
 
     }
 

-  /* All done.  Clean up.  */
-  BITMAP_XFREE (vars);
+  return phi_inserted;

 }
 
 }
 

+/* Helper walking the dominator tree starting from BB and processing
+   phi nodes with global data PHIVN and N.  */

 
 static bool
 
 static bool

-gate_forwprop (void)
+tree_ssa_phiprop_1 (basic_block bb, struct phiprop_d *phivn, size_t n)
+{
+  bool did_something = false; 
+  basic_block son;
+  tree phi;
+
+  for (phi = phi_nodes (bb); phi; phi = PHI_CHAIN (phi))
+    did_something |= propagate_with_phi (bb, phi, phivn, n);
+
+  for (son = first_dom_son (CDI_DOMINATORS, bb);
+       son;
+       son = next_dom_son (CDI_DOMINATORS, son))
+    did_something |= tree_ssa_phiprop_1 (son, phivn, n);
+
+  return did_something;
+}
+
+/* Main entry for phiprop pass.  */
+
+static unsigned int
+tree_ssa_phiprop (void)
+{
+  struct phiprop_d *phivn;
+
+  calculate_dominance_info (CDI_DOMINATORS);
+
+  phivn = XCNEWVEC (struct phiprop_d, num_ssa_names);
+
+  if (tree_ssa_phiprop_1 (ENTRY_BLOCK_PTR, phivn, num_ssa_names))
+    bsi_commit_edge_inserts ();
+
+  free (phivn);
+
+  return 0;
+}
+
+static bool
+gate_phiprop (void)

 {
   return 1;
 }
 
 {
   return 1;
 }
 

-struct tree_opt_pass pass_forwprop = {
-  "forwprop",                  /* name */
-  gate_forwprop,               /* gate */
-  tree_ssa_forward_propagate_single_use_vars,  /* execute */
+struct tree_opt_pass pass_phiprop = {
+  "phiprop",                   /* name */
+  gate_phiprop,                        /* gate */
+  tree_ssa_phiprop,            /* execute */

   NULL,                                /* sub */
   NULL,                                /* next */
   0,                           /* static_pass_number */
   TV_TREE_FORWPROP,            /* tv_id */
   NULL,                                /* sub */
   NULL,                                /* next */
   0,                           /* static_pass_number */
   TV_TREE_FORWPROP,            /* tv_id */

-  PROP_cfg | PROP_ssa
-    | PROP_alias,              /* properties_required */
+  PROP_cfg | PROP_ssa,         /* properties_required */

   0,                           /* properties_provided */
   0,                           /* properties_destroyed */
   0,                           /* todo_flags_start */
   0,                           /* properties_provided */
   0,                           /* properties_destroyed */
   0,                           /* todo_flags_start */

-  TODO_dump_func | TODO_ggc_collect    /* todo_flags_finish */
-  | TODO_verify_ssa,
-  0                                    /* letter */
+  TODO_dump_func
+  | TODO_ggc_collect
+  | TODO_update_ssa
+  | TODO_verify_ssa,           /* todo_flags_finish */
+  0                            /* letter */

 };
 };